You can do the following:
-Watch plenty of Korean love dramas/soaps and be safe in the knowledge that despite the oh-so rough road ahead, it is in the stars of cupid, destiny and all things sweet and ideal for you to meet her again.
-Read plenty of love mangas and picture yourself as the main protagonist who runs into his love-interest 50000x in his lifetime before finally admitting that he loves her at the ripe old age of volume 50 (It's okay, manga characters can live forever)
-Walk the streets of Singapore for eternity with a rough sketch that you've for the past half-year lovingly drawn to detail, asking for her identity and calling publicly for her to return to you
-Create a blog in some Singaporean domain and blog each day about your thoughts of this particular feminine creature. Perhaps she will recall that wonderful-day-where-fate-played-its-card and voila, the circle is complete
-Buy this very practical product:
http://www.youtube.com/watch?v=usbNJMUZSwo Put it to good use and eventually the law of attraction will grant you her, I guess?
-Everytime you go on the MRT whether it's crowded or not, be sure to leave a space with her exact same profile next to you. One day she will see you standing there and remember that wonderful-day-where-fate-played-its-card and voila, the circle is once again complete.
-Since this is a music board, be sure to write an entire album of 12-15 songs about this girl on the train. I'm sure it will be very popular. Among the people in this thread at least. :mrgreen:
-You could of course, realise that the both of you had shoulder-contact (unless by lean, you mean her head had lazily decided to pop itself onto your shoulder which in this case would make the entire case look awkward, not romantic.) and shoulder-leaning is common in all fields of social interaction between women and men, women and women and of course, men and men.
-In case you wish to prepare yourself for the next girl who decides to rest on your shoulder, consider engaging in conversation with every living being you stand or sit next to. In such a scenario, your charisma would be so overwhelming that heads of any female in the vicinity will stick to your shoulder like a magnet.
-Finally, realise that it was such an awesome moment and tell the story to everyone you know. Your respect will receive an upgrade +5. You either talked to her or you didn't, either way it happened. Be proud of it, just don't dwell on it anymore.
Cheers.
(Sorry I have a habit of just making long posts on a spur. Forgive me)